DE4418662A1 - Centrifugal fluid delivery pump impeller - Google Patents

Abstract

An impeller wheel (5) is mounted on a shaft and rotates unidirectionally in a housing drawing fluid through an inlet and out of an outlet. The fluid is moved under the action of several blades (3) which radiate spirally out from the wheel centre toward the outer circumference. The blades have an axial height and are positioned asymmetrically around the wheel centre. The angles between the heads of each blade spiral differ slightly to the neighbouring blade. This causes a reduction in noise and a more smooth operating frequency.

Description

The invention relates to a centrifugal pump according to the one in the preamble of claims 1 and 8 listed features.

Centrifugal pumps of this type are used in a wide variety of for example, also in building technology, such. B. as Heizum roller pumps, or as pumps for domestic waterworks. In addition to one long lifespan and high efficiency are becoming more recent requirements with regard to a possible low noise emissions of such pumps. During this Problem with pumps operating at constant (low) speed is still solvable, arise in modern variable-speed and particularly high-speed centrifugal pump problems. Mechanical piping systems are installed in the house Vibrations in the audible sound range in living areas of the house transferred where they are perceived as stressful.

From DE 39 12 279 C2 it is known to take precautions on the guide apparatus a centrifugal pump to make cavitation problems in this Avoid area. There it is intended to have guiding devices with larger ones Flow openings in the outlet area of the pump. This measure changes the channel flow to cavitation and  to avoid the associated damage to the pump. An influence on the running noise of the pump in normal loading drive is not possible with it.

While in other areas of technology about a Schalliso tried to remedy the situation, succeeds this in the area of the pumps due to the connected rigid Pipe systems only bad. The pump is isolated from vibrations storage is technically complex and also because of the long-term problems with elastic pressure lines are not sufficient desirable.

It is therefore used in the pump sector, especially for heating circulating pumps, the task of creating the noise reduce, and this with as constructively simple means as possible, Because even a little extra effort can be very high for such Units produced units at considerable cost increases to lead.

Noises in pumps are a. by detaching the flow higher flow velocities as well as through the energy transfer generated in the centrifugal pump. That of the rotating shaft Torque transmitted to the impeller is the same great but oppositely directed moment that is at the show fels the impeller and that a special speed distribution of the flow at the impeller outlet causes. The smaller the blade load is the more uniform the flow speed in the pressure side housing behind the impeller where the flow through a more or less trained diffuser is led into the pressure port. This pressure port or also For example, a tongue of the guide apparatus forms for the from the Impeller escaping flow is a point of failure, not just one  Disruption of the flow, but also a Ge noise is generated. This usually results in between Rotary wheel and impurity a mechanical vibration, the reason frequency from the speed of the impeller multiplied by the Number of blades on it calculated. Can be simplified you can imagine the noise development in this area make sure that this separates at the end of the blade a shock wave is generated that strikes the defect, where due to the periodic recurrence a periodic mechanical vibration results, the basic frequency of the usual gyro rotors and rotors commonly used in home technology numbers are in the audible range. It goes without saying that for Ge Noise development also includes other parameters Play role, the noise development described above however, usually for human hearing with its over the Total frequency range of very different sensitivity particularly annoying and perceived as loud noise.

The present invention solves this problem in a genus according centrifugal pump in that for the targeted influencing of in operation from the impeller and / or from the diffuser Ge Noise emissions from the blades of the impeller or the blades of the diffuser related to the axis of rotation of the impeller asym arranged and / or formed metrically. By such Training will not prevent the development of noise as such changes, but is due to the asymmetry of the impeller or No additional periodic pressure increase such as that the vibrations emanating from the individual impeller blades gen in phase and thus add their amplitudes can. The periodi given due to the speed of the impeller Of course, this cannot change the quality.  

Basically, it will be enough if the between the blades formed channels related to the axis of rotation of the impeller asym arranged and / or formed metrically. In practice however, by appropriate training or arrangement of Shovels take place. Since the sound-generating vibrations between Impeller and fault point arise, a change in the off is sufficient tread area of the impeller and / or in the entry area of the guide apparatus.

Such a targeted detuning of the impeller or the guide apparatus This means that there is no longer a uniform fundamental vibration can train, but rather a variety of fundamental vibrations gen arise. In simple terms, instead of be Known fundamental wave generates a frequency band, due to of the different fundamental frequencies an addition of the amplitudes can be practically excluded. The Ge caused by this noise emission is not only significantly lower in amplitude than in known symmetrically constructed gyros or Leitappa guess, but it is also from human hearing itself perceived as more pleasant at comparable sound levels. The before lying invention thus causes a Ver in two respects reduction of noise emissions, on the one hand through objective Reduction of the sound level and secondly by the subjective Frequency distribution that looks more pleasant.

With asymmetrical training or arrangement in the sense of Invention is to be provided that the blades based on the rotation axis of the impeller arranged at different pitch angles are that neighboring blades have a different blade length, So have a different blade shape or that the outlet angles of adjacent blades are different. A running bike with an odd number of congruent blades that are evenly over  distributed around the circumference, so with the same pitch angle, arranged are a symmetrical impeller in the sense of the invention represents.

The above-mentioned options, the Asym to bring about the impeller or the guide apparatus in a targeted manner ren, can also be combined with each other, with such Combinations usually make the result difficult to predict will be. It has proven particularly advantageous to have congruent ones Arrange blades, but to vary the pitch angle α, because then the expected frequency band with sufficient accuracy is predictable.

It has proven particularly favorable to use the pitch angles α - these are the angles at which the blade ends are attached to each other are arranged - so that the inverse value of each part angle multiplied by the value obtained when summing all pitch angle of the impeller results (this is always 360 °), gives a value Z that deviates from an integer. Acoustically particularly favorable pitch angles result when this Value Z from an integer upwards from +0.2 to +0.4 or deviates below. For example, preferred values are for Wheel with seven blades between 7.2 to 7.4 or from 6.6 to 6.8. With regard to the noise emission, this results particularly low values if at least half of all pitch angles these preferred values of Z are met.

In addition, it should be noted that the number Z is the theoretical Bucket number indicates that at the selected pitch angle would result if this were used for all blades. Since the In practice, the number of blades must always be an integer, it is open  obvious that this is only a mathematical quantity acts.

The solution according to the invention is used, for example, in conventional Hei Tension circulation pumps always take place on the impeller side, because of the Housing-shaped diffuser in such pumps usually has no guide vanes and only the flow is spiral transferred into the pressure port. Centrifugal pumps, on the other hand have a diffuser with vanes, as is the case with more stage centrifugal pumps regularly does the emissions reduction also through appropriate training on the guide apparatus, in which, for example, the guide vanes in different pitch angle arranged as described above become.

The invention is based on exemplary embodiments explained in more detail. In a very simplified representation, they show:

Fig. 1 is a plan view of an inventive impeller with congruent blades which are arranged at different pitch angles,

Fig. 2 shows the distribution of the resultant at a defect in the operation of the impeller according to Fig. 1 Grundschwingun conditions (frequency band)

Fig. 3 is a plan view of another embodiment of a drive wheel according to the invention with blades differing length cher,

4 find Fig., A further embodiment of an impeller according to the invention, in which blades with different exit angles use in illustration of FIG. 1,

Fig. 5 is a plan view of a diffuser in which the guide vanes are arranged in different pitch angles and

Fig. 6 is a plan view of a diffuser, in which the guide blades are of different lengths.

The impeller 1 shown in FIG. 1 is shown without a cover plate. It consists of a disc 2 on which seven congruent blades 3 are arranged, which extend from near the impeller axis 4 to the outer periphery 5 of the impeller in the manner shown, where they end. The attachment of such an impeller on the motor axis and the arrangement in the pump housing is known as such and is therefore not described in detail here.

The seven blades 3 are arranged on the disc 2 at different pitch angles α _i . The pitch angle is understood to mean the angle that neighboring blades 3 enclose at the blade end, that is to say on the outer circumference 5 of the impeller 1 . The pitch angle α _i in the wheel 1 shown in FIG. 1 is:

α₁ = 50 °
α₂ = 48.5 °
α₃ = 58 °
α₄ = 46.5 °
α₅ = 53.5 °
α₆ = 47.5 °
α₇ = 56 °.

The actual number of blades Z _impeller is seven. The theoretical number of blades Z described in the introduction, which would result at a certain pitch angle α _i , is for α₁ = 7.2, for α₂ = 7.4, for α₃ = 6.2, for α₄ = 7.7, for α₅ = 6.7, for α₆ = 7.6 and 5α₇ = 6.4. The angles α₁ are so chosen that the number Z deviates by approximately ± 0.2 to 0.4 from any integer Z _g . The pitch angles α₁, α₂, α₄ and α₅ are chosen so that the theoretical wheel numbers Z resulting from these pitch angles deviate by ± 0.2 to 0.4 from the Z _impeller , that is to say more than half of the pitch angles are in this range. Then there is a particularly low noise emission, both in terms of sound level and in terms of frequency distribution.

FIG. 2 shows the frequency band which arises from the above-described impeller shown in FIG. 1 at a fault point in the pump housing when this impeller is driven at 6,000 rpm. The frequency in Hertz and the vertical axis of the sound level are plotted on the horizontal axis of the diagram according to FIG. 2. The resulting frequency band consists of seven, the pitch angles α₁ to α₇ corresponding first harmonic vibrations and numerous (not shown) harmonics, which are however negligible due to the significantly lower sound level. For comparison, the frequency and sound level of three impellers, one with six blades (Z _impeller = 6), one with seven blades (Z _impeller = 7) and one with eight blades (Z _impeller = 8) are shown, with symmetrical Blade arrangement. From the diagram of Fig. 2 it can be easily seen that on the one hand the sound level when using conventional impellers with symmetrical division is more than twice as high as that shown with reference to Fig. 1 and also that instead of a frequency with the Fre an impeller according to Fig. 1, a frequency band is generated, which is perceived by the human ear subjectively more pleasing than a sound with only one frequency, but the same sound level.

Referring to Fig. 3, an impeller 6 is shown, in which the spectacle feln 7 are indeed arranged at the same pitch angle, however, have different lengths. This impeller also has a disc 2 , which is rotatable about an axis 4 , on which the individual blades 7 are arranged. The blades 7.1 to 7.7 have a different length, and in the present exemplary embodiment the blade 7.2 has a length of 70.42 mm, the blade 7.4 a length of 65.73 mm, the blade 7.6 a length of 66.85 mm and the blade 7.7 has a length of 68.64 mm. The other blades 7.1 , 7.2 , 7.3 and 7.5 (not numbered in detail in FIG. 3) likewise have different lengths. By this asymmetry, a similar detuning is achieved in that not a fixed frequency, but a frequency band of lower sound level is generated with the impeller when rotating at an impurity.

Fig. 4 shows an impeller 8 , with the blades 9, the exit angle β of the individual blades are selected differently. These angles β, of which the angles β 1, β 2 and β 3 are shown by way of example in FIG. 4, are in the embodiment shown:

β₁ = 48 °
β₂ = 40 °
β₃ = 21 °

The exit angles of the other blades are also different Lich.  

The exit angle β is the angle that the blade end 10 forms at this point with a tangent 11 of an imaginary circle about the impeller axis 4 .

Instead of the specific detuning described above as an example of the impeller or additionally, a corresponding Ver on the guide apparatus in order to reduce the loading to achieve drive noise. Such, surrounding the impeller Guide devices are well known and are therefore not described here described.

In Fig. 5, a guide device 12 is shown, which has seven congruent guide vanes 13 , which are arranged with respect to the axis 4 of the guide apparatus at different pitch angles α ' _i . The pitch angle is to be understood in accordance with the definitions given above for the impeller. . In the embodiment of Figure 5, the pitch angles are α _'i:

α'₁ = 46 °
α'₂ = 53 °
α′₃ = 47 °
α′₄ = 56 °
α′₅ = 50 °
α′₆ = 48 °
α′₇ = 58 °.

The relationships of the pitch angle to the theoretical number of blades Z described at the beginning and explained by way of example using the impeller according to FIG. 1 apply accordingly to the guide device 12 .

In the guide device 14 shown in FIG. 6, 8 guide vanes 15 are provided, which are arranged at the same pitch angle α ', but have different lengths. The sixth guide vane 15.6 has a length of 46.4 mm, the seventh guide vane 15.7 has a length of 73.2 mm and the eighth guide vane 15.8 has a length of 44.6 mm. Such a targeted detuning of the guide apparatus by changing the lengths of the individual guide vanes 15 is comparable to the design of the impeller 6 described with reference to FIG. 3.

The impellers and nozzles described above are special for centrifugal pumps with variable-speed drive motors seen, for example for frequency converter controlled pumps aggregates.

Reference list

1 - impeller
2 - disc
3 - shovels
4 -axis
5 - outer circumference
α _i pitch angle
Z - theoretical number of blades at a division angle α _i
Z _impeller actual number of blades
Z _g - integer
6 - impeller Fig. 3
7 - blades ( 7.2 , 7.4 , 7.6 and 7.7 )
8 - impeller Fig. 4
9 - shovels
10 - bucket end
11 - tangent
12 - diffuser Fig. 5
13 - guide vanes
α ′ _i pitch angle
14 - diffuser Fig. 6
15 - guide vanes ( 15.6 , 15.7 , 15.8 )

Claims (14)

1. Centrifugal pump with at least one impeller ( 3 ; 7 ; 9 ) provided with blades ( 1 ; 6 ; 8 ), characterized in that the blades ( 3 ; 7 ; 8 ) have a targeted influence on the noise emissions during operation from the impeller ( 1 ; 6 ; 8 ). 3 ; 7 ; 9 ) of the impeller and / or the channels formed between the blades are arranged and / or configured asymmetrically with respect to the axis of rotation ( 4 ). 2. Centrifugal pump according to claim 1, characterized in that the distances from the blade ends of adjacent blades ( 3 ; 9 ) are of different sizes. 3. Centrifugal pump according to claim 1 or 2, characterized in that the blades ( 7 ) of the impeller ( 6 ) have different lengths. 4. Centrifugal pump according to one of the preceding claims, characterized in that the, preferably all blades ( 3 ) are arranged at different pitch angles α on the impeller ( 1 ). 5. Centrifugal pump according to one of the preceding claims, characterized in that all the blades ( 3 ) of the impeller ( 1 ) are congruent. 6. Centrifugal pump according to one of the preceding claims, characterized in that each of the pitch angle α is chosen so that its inverse value multiplied by that of the sum of all pitch angles of the impeller ( 1 ) results in a number Z which is not equal to an integer number Z _g : 7. Centrifugal pump according to one of the preceding claims, characterized in that at least half the pitch angle α of the impeller ( 1 ), the number Z deviates by 0.2 to 0.4 from the actual number of blades Z _impeller : Z = Z _impeller ± (0.2 to 0.4). 8. Centrifugal pump with at least one impeller and one with vanes ( 13 ; 15 ) provided with the guide device ( 12 ; 14 ), characterized in that the blades ( 13 ; 15 ) of the guide apparatus ( 12 ; 14 ) and / or the channels formed between the blades are arranged and / or configured asymmetrically with respect to the axis of rotation ( 4 ) of the impeller. 9. Centrifugal pump according to claim 7, characterized in that the distances between the blade ends facing the impeller Blades of the diffuser are of different sizes.   10. Centrifugal pump according to one of the preceding claims, characterized in that the blades ( 15 ) of the diffuser ( 14 ) have different lengths. 11. Centrifugal pump according to one of the preceding claims, characterized in that the, preferably all blades ( 13 ) of the diffuser ( 12 ) are arranged at different pitch angles α '. 12. Centrifugal pump according to one of the preceding claims, characterized in that all blades ( 13 ) of the diffuser ( 12 ) are congruent. 13. Centrifugal pump according to one of the preceding claims, characterized in that each of the pitch angle α 'is chosen so that its inverse value multiplied by that of the sum of all pitch angles of the nozzle ( 12 ) results in a number Z', which is un equal to an integer Z _g is: 14. Centrifugal pump according to one of the preceding claims, characterized in that the number Z deviates by +0.2 to +0.4 or by +0.6 to +0.8 from an integer number Z _g upwards.